A method of fabricating a semiconductor device includes the steps of forming, for example, a poly-Si layer and a metal layer of a metal, such as Al, W, Cu or such, on a semiconductor wafer. A CVD process is one of processes of forming such layers.
When forming a desired film on a semiconductor wafer by a single-wafer CVD process, the semiconductor wafer is supported on a susceptor placed in a processing chamber. A shield ring is put on the susceptor so as to surround the semiconductor wafer. Prevalently used susceptors and shield rings are those of amorphous carbon or sintered SiC or those formed by coating with a CVD-SiC material.
When depositing a film on a semiconductor wafer by a CVD process in a reaction chamber, the reaction chamber is filled with reactive process gases. Consequently, a film is deposited on parts including the susceptor and the shield ring placed in the reaction chamber as well as on the semiconductor wafer. Thus, the parts placed in the reaction chamber must be cleaned after processing a predetermined semiconductor wafers by a film deposition process.
Generally, the interior of the reaction chamber is cleaned by a wet cleaning method using an acid or alkaline solution. When cleaning the reaction chamber by the wet cleaning method, the film forming system including the reaction chamber must be stopped and the parts must be removed from the reaction chamber. The wet cleaning method takes time and reduces film-forming efficiency. When depositing a film on a semiconductor wafer after removing the parts from the reaction chamber, cleaning the same and returning the same into the reaction chamber, it is possible that impurities adhere to the semiconductor wafer. The impurities adhering to the semiconductor wafer affect adversely to products and reduce the life of the parts.
Recently, an in-situ dry cleaning method using a halogen-containing cleaning gas, such as ClF3 gas, is used to solve problems that may be caused by the wet cleaning method. The dry cleaning method cleans the parts without removing the same from the reaction chamber by supplying a cleaning gas, such as ClF3 gas.
However, during the cleaning of the parts including a susceptor of sintered SiC by the dry cleaning method using ClF3 gas or the like, ClF3 gas etches a sintering agent bonding SiC particles together and, consequently, the particles of SiC separate. Thus, the sintered SiC parts have unsatisfactory corrosion resistance and are practically incompetent. An amorphous carbon part is superior in corrosion resistance to a sintered SiC part. However, amorphous carbon reacts with ClF3 gas, a CF film is deposited on the surfaces of the parts including a shower head and placed in the reaction chamber, and the CF film comes off the surfaces of the parts in particles occasionally. The particles contaminate the semiconductor wafer, reducing the yield rate of the product.
Corrosion resistance of parts including a susceptor formed by coating blanks with a CVD-SiC material is more satisfactory than that of parts of sintered SiC, and the parts formed by coating blanks with a CVD-SiC material do not cause problems that may be caused by parts formed of amorphous carbon. However, the surfaces of the parts formed by coating blanks with a CVD-SiC material are subject to etching and hence the life of those parts is short. The SiC material is easily etched, and the SiC material is liable to be reduced to particles, which reduces the yield rate.
The uniformity of the surface of the conventional CVD-SiC material is not necessarily satisfactory, and a CVD-SiC material having a uniform surface has been desired.